Abstract
Accumulation and deposition of β-amyloid protein (Aβ) are the hallmark features of Alzheimer's disease. The inhalation anesthetic isoflurane has been shown to induce caspase activation and increase Aβ accumulation. In addition, recent studies suggest that isoflurane may directly promote the formation of cytotoxic soluble Aβ oligomers, which are thought to be the key pathological species in AD. In contrast, propofol, the most commonly used intravenous anesthetic, has been reported to have neuroprotective effects. We therefore set out to compare the effects of isoflurane and propofol alone and in combination on caspase-3 activation and Aβ oligomerization in vitro and in vivo. Naïve and stably-transfected H4 human neuroglioma cells that express human amyloid precursor protein, the precursor for Aβ; neonatal mice; and conditioned cell culture media containing secreted human Aβ40 or Aβ42 were treated with isoflurane and/or propofol. Here we show for the first time that propofol can attenuate isoflurane-induced caspase-3 activation in cultured cells and in the brain tissues of neonatal mice. Furthermore, propofol-mediated caspase inhibition occurred when there were elevated levels of Aβ. Finally, isoflurane alone induces Aβ42, but not Aβ40, oligomerization, and propofol can inhibit the isoflurane-mediated oligomerization of Aβ42. These data suggest that propofol may mitigate the caspase-3 activation by attenuating the isoflurane-induced Aβ42 oligomerization. Our findings provide novel insights into the possible mechanisms of isoflurane-induced neurotoxicity that may aid in the development of strategies to minimize potential adverse effects associated with the administration of anesthetics to patients.
Highlights
Alzheimer’s disease (AD) is one of the most common forms of dementia, which affects 4.5 million Americans and costs more than $100 billion a year on direct patient care alone
These findings suggest that caspase activation alone without apoptosis may still be able to contribute to AD neuropathogenesis
The propofol treatment attenuated the isoflurane-induced caspase-3 activation: 2.30 fold versus 1.77 fold (P = 0.005). These findings suggest that propofol may mitigate the isoflurane-induced caspase-3 activation in H4-amyloid precursor protein (APP) cells
Summary
Alzheimer’s disease (AD) is one of the most common forms of dementia, which affects 4.5 million Americans and costs more than $100 billion a year on direct patient care alone. Increasing evidence suggests a role for caspase activation and apoptosis in AD neuropathogenesis ([2,3,4,5,6,7,8, 9,10,11], reviewed in [12,13]). A recent study by Burguillos et al [14] have shown that pro-inflammatory stimuli, e.g., lipopolysaccharide, can induce the activation of caspase-8, -3 and -7 inside microglia without causing apoptosis. The activated caspases have been found in the frontal cortex of AD patients. Taken together, these findings suggest that caspase activation alone without apoptosis may still be able to contribute to AD neuropathogenesis
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